Barrel collet for mechanical pencils



Patented Nov. 1, 1949 UNITED STATES PATENT OFFICE BARREL COLLETFOR/MECHANICAL PENCILS Application March 1, 1946, Serial No. 651,207

4 Claims.

This invention relates to improvements in barrel collets for mechanicalpencils.

In Patent No. 2,358,091 of September .12, 1944, I have disclosed amechanical pencil in which the rod of lead is fed, step by step, bysimple pressings and releasings of an exterior part of the pencil.Within the barrel is a collet having resiliently flexible prongs thatrub on the rod, pointing a little forward from perpendicularity to therod. These can bend to let the lead slip forward easily, but if the leadbegins to move backward they jam between the lead and the barrel and soarrest regression of the lead. The present invention providesan improvedstructure of collet which ma be used in that pencil, and can be usedmother constructions of pencil, for permitting progression and,preventing regression of the lead.

This invention eliminates the requirement that the prongs be made ofmaterial which is inherently resilient. Also zit dispenses with annularintegral supports for their ends. It permits of the prongs being stamped.from 'thin plane nonelastic sheets, and of their being assembledloosely without further treatment. making the'bi-ts in T-shape, itprovides 'fortheir being held in ready position, withoutclosing .theaxial hole when the barrel is empty of lead. These bits are combinedwith an annular shoe, backed by a simple helicalspring, those yieldinglets the lead-engaging ends of .the,prongs.swing 'forward'whendraggedby'forward feedingof the lead, but pushes them gently back intojam position endwise ibe'tween the lead and-the peripheral wall, to-oppose regressionpfthe lead, withoutiit being necessary that the prongsshould *bend to allow forward movement, ."and become stifi in backwardmovement.

By this means uniformity of elasticity is assured in the prong action,both among those prongs that are assembled in a single pencil, and alsoamong the assemblies of prongs in individual pencils that are made inmass production. Also, the invention facilitates the producing of anydesired degree of resilience in the action of the prongs, whatever maybe the size or the nature of the material composing the writing rod.Other advantages are that the durability of this important part of amechanical pencil is increased; the processes of manufacture of thecollet are simplified; and the costs are reduced.

Details of an illustrative construction, by which these benefits areattained, are shown in the accompanying drawing, in which And, by

Figure 1 is a medial longitudinal section through a mid-portion of amechanical pencil containing the barrel collet of the invention; and

Figure 2 is .a cross-section through the collet portion of Figure 1 on.a line 22 that passes between prongs.

For both figures the scale is greatly enlarged. While the inventionisapplicable to pencils of an size, it in particular is intended forpencils of ordinary size whose outside diameter .is ;a minor fraction ofan inch.

In a complete pencil the prongs ID of the collet are housed within ashell l2, which has annular walls within which an annular ledge i3surrounds adeep well M. This shell 12 has .an

insetlid l6, and islhere represented as being fixed seated at thejunction of the cylindrical and the tapering pointparts of thebarrelbyamain operating spring 2'!) which bears downward around a boss .22 onthe lid [8 and bears upward against an upper part (not shown) of .a longtube 24 that surrounds the lead 25. When the user presses this tube 125,by thumb pressure on its top, a collet at the bottom (not shown) gripsand feeds the lead 26 a step downward, as can be seen in my said'Patent2,358,091.

The function .of the barrel collet prongs IEI is to let thelead 26 befed downward easily, but to oppose its moving upward. The tube 24 passesloosely through the shell 12 of the barrel collet. At the regionillustrated, .the lead 26 .is loose within that tube. Slots .38 in thetube '24 provide ample clearance for the barrel collet prongs ID toreach the lead. The prongs may be a single opposed pair, or, maybebanked in multiple behind one another as illustrated, .arranged on twoormore sides of the lead, all operating together .as .a unit; lbutin.either case 'there are stiiT bits of sheet material confined loosely inradial grooves, within housing [2. They point a little forward ofperpendicularity to the axis, the angle illustrated being about 5. Thisangle might be greater or less, the critical feature be ing that eachprong has length exceeding the radial distance from the side wall of thehousing !2 to the rod of lead, and is too stifi to buckle past theperpendicular, when pressed upward by the lead.

As can be understood from the drawing, the

to fill the housing I 2 with an annular mass or body, of material, hereshown as a boss on the lid I6 within the housing, in which there are twoopposite radial recesses 34, each broad and high enough to contain andto hold loosely a group of the prongs Hi. There is also an annularperipheral groove 36 on the peripheral outside of this mass, connectingwith the radial recesses 34. The prongs are of T-shape, and the flangesof the head of each are engaged in the peripheral recess 36. Thus eachT-head abuts the outer wall of the shell l2; and the leg of each Textends within a recess 34, and through a slot 38 in the tube 24, forits concave-ended foot to engage the rod of lead 26. Each individualprong fits loosely in these interior spaces. with the mid-portion of thegroup of prongs supported on the shoe 46, except that the length of eachprong slightl exceeds the space which is open radially for housing it.Therefore each prong pitches slightly forward, in the direction ofdownward feed of the lead; but this pitch is held to a minimum by theannular shoe 4!! pressed upward by a mild helical spring 44 that isstrung on the sleeve 42 and is based on the bottom of the well 38.Therefore the prongs normally stand always in contact both with thehousing shell 12 at their heads and with the rod of lead 26 at theirfeet. When the lead 26 is fed downward by the user of the pencil thespring 44 yields to let the prong feet that are in contact with the leadbe dragged slightly downward, increasing their pitch and easing themovement of the rod of lead. At the same time the lid l6 prevents thehead ends of the prongs from being lifted by the spring 44. But if thelead 26 begins to move upward, either by drag of the tube 24 inreturning after being released by the users thumb, or by pressure of thepoint of the lead on paper in writing, the drag is in direction toincrease the friction between the lead and the feet of the prongs, andis aided by the spring 44 and its shoe 2! to make a jam of the prongsbetween the lead and the housing. Thus an incipient recession of thelead moves the prongs toward perpendicularity to the axis, with increaseof friction and with operative opposition to more than incipient upwardmovement of the lead.

The collet prongs fit into their housing loosely enough to perform thesemovements without becoming stuck, and yet the shoe 40 always makes themtight enough to catch on the lead and oppose the upward movement of thelead relative to the barrel, as thus described. The prongs are preferablmade of non-corrosive material. The flanges at their heads prevent themfrom slipping into the central hole when the lead is absent, and thisdevice to hold their heads at the periphery dispenses with the need formaking them integral parts of washers having continuous annular rims,leaving each of them free to rise and fall and shift its angle withinthe very small limits available, without requiring that there be aflexibility or any uniformity of resilience in the prongs themselves,all of which are preferably so stiff that they do not bend appreciably.While the drawing shows a considerable number of prongs in the assemblyat each side of the lead, and shows them arranged in two opposing groupson a single diameter. construction is not limited in either of theserespects, the radial directions in which the slots 34 extend, and thenumber of prongs assembled in each, being matters of choice.

I claim:

1. A collet for opposing regression of an axial rod of lead, comprising,in combination a bottomed shell with an axial hole for the rod; prongshoused by the shell; an annular mass of material Within the shell,having an axial hole for said rod, and having radial recesses with sidewalls which lead from that axial hole to the peripheral wall of theshell; said prongs being bits of thin stiff sheet material set looselyin the recesses and having radial extent which slightly exceeds theradial distance from the axia1 hole to the peripheral wall of the shell;and a spring,

within the shell, based on the bottom of the shell and set to press theaxial ends of the prongs backward into said hole.

2. A barrel collet as in claim 1, further characterized in that thereare mutually obstructive surfaces, on said mass and on said bitsrespectively, within the shell, arranged to limit movement of the loosebits toward the axis, thereby to hold the bits from closing the axialspace.

3. A barrel collet as in claim 1, further characterized in that the bitsare of T-shape, and there is peripheral space around said mass,connected with said recesses, for housing the heads of the T-bits,whereby the loose bits are restrained from filling the axial hole.

4. A barrel collet as in claim 1, in which the shell has a well belowthe prongs, and in the well there is a loose sleeve having an annulartop shoe to engage the bits, the said spring being helical, strung onthe sleeve, and based on the bottom of the well.

CHARLES K. LOVEJOY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,179,835 Ward Nov. 14, 19392,190,798 Morlock Feb. 20, 1940 2,358,091 Lovejoy Sept. 12, 19442,385,329 Buchanan Sept. 25, 1945 I i l 1

